Stimulated echo acquisition mode (STEAM) diffusion tensor imaging with different diffusion encoding times in the supraspinatus muscle: Test-retest reliability and comparison to spin echo diffusion tensor imaging

Diffusion tensor imaging (DTI) provides insight into the skeletal muscle microstructure and can be acquired using a stimulated echo acquisition mode (STEAM)-based approach to quantify time-dependent tissue diffusion. This study examined diffusion metrics and signal-to-noise ratio (SNR) in the supraspinatus muscle obtained with a STEAM-DTI sequence with different diffusion encoding times (Delta) and compared them to measures from a spin echo (SE) sequence. Ten healthy subjects (mean age 31.5 +/- 4.7 years; five females) underwent 3-Tesla STEAM and SE-DTI of the shoulder in three sessions. STEAM was acquired with Delta of 100/200/400/600 ms. The diffusion encoding time in SE scans was 19 ms (b = 500 s/mm(2)). Region of interest-based measurement of fractional anisotropy (FA), mean diffusivity (MD), and SNR was performed. Intraclass correlation coefficients (ICCs) were computed to assess test-retest reliability. ANOVA with post-hoc pairwise tests was used to compare measures between different Delta of STEAM as well as STEAM and SE, respectively. FA was significantly higher (FA(STEAM): 0.38-0.46 vs. FA(SE): 0.26) and MD significantly lower (MDSTEAM: 1.20-1.33 vs. MDSE: 1.62 x 10(-3) mm(2)/s) in STEAM compared to SE (p < 0.001, respectively). SNR was significantly higher for SE (72.3 +/- 8.7) than for STEAM (p < 0.001). ICCs were excellent for FA in STEAM (>= 0.911) and SE (0.960). For MD, ICCs were good for STEAM(100ms-600ms) (>= 0.759) and SE (0.752). STEAM and SE exhibited excellent reliability for FA and good reliability for MD in the supraspinatus muscle. SNR was significantly higher in SE compared to STEAM.